Low Noise, Low Power Cavity Optomechanical Oscillators

Alejandro Grine

Cavity Optomechanical oscillators (OMOs) rely upon photon radiation pressure to induce harmonic mechanical motion of a micron-scale light resonator. Unlike most oscillators, optomechanical oscillators require only CW input light without the need for electronic feedback and so hold promise for their novelty. In an optical cavity of sufficient quality factor, the transduction from photons to phonons can be quite efficient as we characterized optomechanical cavities which only required 17 microwatt input optical power to induce mechanical oscillation. The question then remains whether OMOs can be made low noise and of course better yet, low noise and low power.

By characterizing various materials and designs, it is shown that indeed OMOs may be made low noise and low power through maximization of the mechanical quality factor – a common quest for MEMs designers. With an emphasis on wafer-scale processes on silicon substrates, OMOs constructed from reflowed phosphosilicate glass, silicon nitride, and silicon were characterized and modeled. Due to non-linear light-matter interactions, OMOs are also known to produce RF frequency combs with an optical carrier. These combs were investigated and a method to produce a frequency comb spanning more than 6GHz from a 52MHz carrier was found. As a demonstration for how an OMO may be utilized in a chip-scale atomic clock, the 9th harmonic of a voltage-tunable device was phase-locked to a low noise microwave reference resulting in an 85dB reduction in phase noise at 1Hz offset from the carrier.

Advisor: Ming C. Wu

BibTeX citation:

@phdthesis{Grine:EECS-2016-179,
Author = {Grine, Alejandro},
Title = {Low Noise, Low Power Cavity Optomechanical Oscillators},
School = {EECS Department, University of California, Berkeley},
Year = {2016},
Month = {Dec},
URL = {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2016/EECS-2016-179.html},
Number = {UCB/EECS-2016-179},
Abstract = {Cavity Optomechanical oscillators (OMOs) rely upon photon radiation pressure to induce harmonic mechanical motion of a micron-scale light resonator. Unlike most oscillators, optomechanical oscillators require only CW input light without the need for electronic feedback and so hold promise for their novelty. In an optical cavity of sufficient quality factor, the transduction from photons to phonons can be quite efficient as we characterized optomechanical cavities which only required 17 microwatt input optical power to induce mechanical oscillation. The question then remains whether OMOs can be made low noise and of course better yet, low noise and low power.
By characterizing various materials and designs, it is shown that indeed OMOs may be made low noise and low power through maximization of the mechanical quality factor – a common quest for MEMs designers. With an emphasis on wafer-scale processes on silicon substrates, OMOs constructed from reflowed phosphosilicate glass, silicon nitride, and silicon were characterized and modeled. Due to non-linear light-matter interactions, OMOs are also known to produce RF frequency combs with an optical carrier. These combs were investigated and a method to produce a frequency comb spanning more than 6GHz from a 52MHz carrier was found. As a demonstration for how an OMO may be utilized in a chip-scale atomic clock, the 9th harmonic of a voltage-tunable device was phase-locked to a low noise microwave reference resulting in an 85dB reduction in phase noise at 1Hz offset from the carrier.}
}